This invention relates to fault detectors and, more particularly to a faulted fuse detector for an inverter connected to strings of photovoltaic panels.
A conventional photovoltaic power circuit typically includes a plurality of photovoltaic (PV) strings connected to an inverter. Each PV string is comprised of a plurality of PV panels that be connected together in series and/or parallel. The PV panels are operable to generate DC current from solar radiation. Each PV string has both a positive lead and a negative lead. An inverter typically can accept between 1 and 4 string inputs, depending on the power levels involved. Each PV string is usually protected from an over-current condition, typically with so-called string fuses. These string fuses are designed to safely open under a fault condition. Typically, under such a fault condition, an element within the fuse will melt and open up, thus interrupting the flow of fault current. For more robust protection levels, both the positive and negative string leads are fused.
The inverter can only output maximum power when all PV strings are producing power to the input of the inverter. If one string has a fault and the fuse opens, the output power level of the inverter will be significantly reduced. Often, the fault goes undetected, and the inverter continues to run, albeit at a much lower output power level, which is uneconomical.
Based on the foregoing, there is a need in the art for a detector that is operable to detect faulted fuses in PV strings connected to an inverter. The present invention is directed to such a detector.